1. Field of the Invention
The present invention relates to a vertical bidirectional power switch controlled by high-frequency signals (HF).
2. Discussion of Prior Art
Among switches intended to switch high voltages, and especially to switch loads connected to the mains voltage, vertical switches with four semiconductor layers of alternate conductivity types, generally designated as SCRs (Silicon Controlled Rectifiers), are essentially used. Among SCR switches, the most current are thyristors, which are unidirectional switches, and triacs, which are bidirectional switches. A conventional triac is formed of a semiconductor chip having its rear surface covered with a single metallization corresponding to a first main electrode and having its front surface covered with a metallization corresponding to a second main electrode and with a metallization to which a control terminal or gate is connected. A disadvantage of conventional triacs is that, for the control, a signal which is referenced to the front surface electrode must be applied to the gate. Now, in practice, such components are assembled by welding of their rear surface to a radiator, and this radiator is generally grounded. However, an A.C. voltage, for example, the mains voltage, is present on the front surface of the triac, and the control voltage must thus be applied in reference to a variable voltage. Since the control signal for example originates from an integrated circuit, this poses problems of isolation between this integrated circuit and the mains voltage.
Thus, the Applicant has created the concept of a bidirectional switch in which the control signal is referenced to the rear surface electrode. The Applicant sells this component under trademark “ACS” and has carried out many studies on such components. U.S. Pat. Nos. 6,034,381, 6,593,600, and 6,927,427 may especially be mentioned. For the sake of brevity, this type of switch will be called “rear surface reference switch” hereafter.
Further, the applicant has carried out many studies and implementations on the control of SCRs with high frequencies (HF or RF). This is the specific object of U.S. Pat. Nos. 6,862,196, 7,612,387, and patent application Ser. No. 11/643,444. These documents do not discuss rear surface reference switches, but rather thyristors and triacs. The various RF control systems of SCRs imply the use of one or several diodes having an electrode connected to a terminal of the SCR. Given that these diodes must let through high frequencies, it is preferable to use Schottky diodes, which are faster than bipolar diodes.
Of course, these diodes are desired to be integrated in the power component chip to avoid having to assemble a discrete diode. To this day, a solution has been found to perform this integration in the case where the SCR is a thyristor, as provided in above-mentioned U.S. Pat. No. 7,612,387.